Chemical decomposition of epoxy resin in near-critical water by an acid-base catalytic method

Chemical decomposition of an epoxy resin (E-51) cured with methyl tetrahydro phthalic anhydride (MeTHPA) in near-critical water conditions was investigated under different concentrations of acid-base catalyst. The optimal catalytic concentration of KOH catalyst ranged from 0.5 mol L-1 to 1.0 mol L-1, while that of H2SO4 catalyst was 0.4 mol L-1. Meanwhile, the decomposition ratio of the E-51/MeTHPA system could reach up to 97.7-100%. In addition, FT-IR results of the solid residue of the E-51/MeTHPA system before and after near-critical water treatment showed that the changes of the molecular structure were mainly reflected in the changes of the relative contents of mixed ether bonds, crosslinked bonds and other functional groups. The decomposition products in the acetone phase were identified by GC-MS. The results suggested that the main compositions and relative peak areas of the decomposition products varied with the change of the concentration of acid-base catalyst. Finally, a possible decomposition reaction mechanism was proposed for the E-51/MeTHPA system.